Transcript Developmental Brain Ontogeny

Developmental Brain
Ontogeny
Developmental
Neuropsychology
Gyri Formation
Originally thought to reflect a
passive process
– Mechanical folding
– Early brain is smooth or
lessencephalic
– Neurons migrate from the germinal
matrix
– Dorsolateral side of lateral
ventrilces
Gyri Formation
Gyral patterns can be modified
experimentally
– Lesions yield abnormal patterns
– Microgyria and cytoarchitectonic
abnormalities results from brain
injury
Fetal Brain Development
Neural tube first recognizable
structure
– Occurs about 6-8 weeks gestation
– Begins to differentiate
– Bulb at anterior end
Fetal Brain Development
Neural tube is the first
recognizable structure
– Bulb develops lateral fissure
– Sylvian fissure develops downward ascending
Fetal Brain Development
Approximately recognizable
brain at 3-4 months gestation
No cortical processes at this
point
At 7-8 months gestation 6 layers
of the cortex appear
Brain Development
Head size increases
Density of cells decreases, size
increases
Myelination occurs for life
Cortex develops from the
bottom up
Brain Development
Fissures
– Parietal, occipital, temporal in the
first two years
– Frontal spurt ages 2 to 6
Brain Development
Electrophysiology
– 1st year delta predominates
• (1.5 to 3.5 HZ)
– 6+ alpha increases
• (7.5 to 12.5 HZ)
Fetal Brain Development
Neurons seem to “know” their
final location and migrate
Myelination – development of
white fatty sheath, covers most
neurons continues well into life
Developmental Brain
Development
Newborn 6 months 2 years Adult
Density
(x103/mm3)
99
30.5
20.1
12.5
Cell Volume
(um3)
240
610
990
1040
Dendritic
branches
3.1
15.6
16.7
40.8
Dendritic
length (um)
203
2367
3259
6836